Technical Field
The present disclosure relates to systems and methods for dissolving cellulose. In particular, the present disclosure provides processes for dissolving modified cellulose to provide solutions having thixotropic properties. The thixotropic solutions are useful in embolization and other medical procedures.
Background of Related Art
Cellulose is the most abundant biorenewable material, and cellulose-derived products have been used in multiple industries, including manufacturing of textiles and medical devices. Apart from the use of unmodified cellulose-containing materials (for example wood, cotton), modern cellulose technology requires extraction and processing of cellulose from primary sources using techniques that have changed very little since the inception of the modern chemical industry.
The full potential of cellulose and cellulose products has not been fully exploited, partially due to the historical shift towards petroleum-based polymers, and also by the limited number of common solvents in which cellulose is readily soluble. Traditional cellulose dissolution processes, including the cuprammonium and xanthate processes, are often cumbersome or expensive and require the use of unusual solvents, typically with a high ionic strength, under relatively harsh conditions.
Various processes for dissolving cellulose have been previously disclosed. See, for example, McCormick, et al. “Solution Studies of Cellulose in Lithium Chloride and N,N-Dimethylacetamide,” Macromolecules, 1985, Vol. 18, No. 12, 1985, pp. 2394-2401; Timpa, “Application of Universal Calibration in Gel Permeation Chromatography for Molecular Weight Determination of Plant Cell Wall Polymers: Cotton Fiber,” J. Agric. Food Chem., 1991, 39, 270-275; and Strlič et al., “Size Exclusion Chromatograhy of Cellulose in LiCl/N,N-Dimethylacetamide,” J. Biochem. Biophys. Methods, 2003, 56, pp. 265-279.
Improved processes for dissolving cellulose, that overcome the need for high thermal treatment, excessive physical manipulation (e.g., stirring), and/or lengthy treatment periods, all of which contribute to the degradation of the cellulose and removal of oxidized groups from oxidized cellulose, remain desirable.